JP2010103635A - Dual-frequency antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dual-frequency antenna device, capable of covering a wide area by increasing the communication distance in a UHF band and which can be miniaturized. <P>SOLUTION: A matching device case 21 for a matching device 20 is grounded by a pile 22, and a VHF antenna 30 and a UHF antenna 40 are provided on the matching device case 21. With respect to the UHF antenna 40, a center conductor 33 of a coaxial tube 31 is protruded to a prescribed length, upward from an upper end of an external conductor 32 to form a radiating element, and a ground wire element is provided in two stages on the external conductor 32, whereby a Brown antenna is constituted. With respect to the VHF antenna 30, an external conductor 32 of a coaxial tube 31 having a prescribed length is used as a radiating element to constitute a monopole antenna with the ground surface as the ground. The external conductor 32 of the coaxial tube 31 is power-fed through the matching device 20 in the VHF antenna 30. To the UHF antenna 40 power-feeding is carried out via the matching device 20 and the external conductor 32 of the coaxial tube 31. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dual-frequency antenna apparatus having characteristics of a vertically polarized omnidirectional antenna and used for wireless communication or the like as a simple installation type base station.

  For example, when installing a simple installation type base station that uses radio waves in the VHF band and the UHF band, it is necessary to install antennas in the VHF band and the UHF band, but it takes time to install separate antennas in the VHF band and the UHF band. There are problems such as selecting the installation location of the antenna. For this reason, as the antenna for the simple installation type base station, a dual-frequency antenna that can share the frequency of the VHF band and the UHF band with one antenna is conventionally used.

As a dual-frequency antenna that can share the frequencies of the VHF band and the UHF band, there are conventionally a monopole antenna with a ground as a ground and a monopole antenna with a ground wire (brown antenna) in which ground wires are horizontally provided. (For example, refer to Patent Document 1)
In the monopole antenna with the ground as the ground, as shown in FIG. 13, the monopole UHF antenna 11 and the VHF antenna 12 are arranged linearly in a direction perpendicular to the ground 14, and the loading element 13 is interposed between them. Is provided. In this case, the UHF antenna 11 is disposed on the lower side, the VHF antenna 12 is disposed on the upper side, and power is fed from the power feeding unit 15 provided at the lower part of the UHF antenna 11. By arranging the UHF antenna 11 on the lower side and the VHF antenna 12 on the upper side as described above, matching can be easily achieved and reflection loss is reduced.

  However, in the UHF band with a short wavelength, when the UHF antenna 11 is provided on the lower side, there is a problem that the line-of-sight distance becomes shorter and the communication distance becomes extremely shorter than when the UHF antenna 11 is provided on the upper side.

  Also, a monopole antenna with a ground wire (brown antenna) with ground wire elements provided in the horizontal direction has a length of one ground wire of about λ / 4 (λ: wavelength of the used frequency), and the antenna becomes large. Therefore, when used in a simple installation type base station, there is a problem such as injuries with a ground line extending laterally during assembly.

Further, as a known technique related to the present invention, in the conical monopole antenna used in the medium wave band and the short wave band, the length of the support is shortened to about 1/20 wavelength of the minimum use frequency band, A technique is known in which, by adding a coil, a ground wire element, etc., a wide band characteristic is provided, and a horizontal stay is not required, so that opening and withdrawal operations can be easily performed (see, for example, Patent Document 2). .
Japanese Patent Laid-Open No. 9-93026 Japanese Utility Model Publication No. 5-36916

  The conventional dual-frequency antenna of the monopole antenna shown in FIG. 13 has a UHF antenna 11 on the lower side and a VHF antenna 12 on the upper side because of the relationship between matching and reflection loss. In the short UHF band, radio wave propagation by diffracted waves is basically not performed. Therefore, when the UHF antenna 11 is provided on the lower side, there is a problem that the communication distance becomes extremely short as compared with the case where the UHF antenna 11 is provided on the upper side. .

  In addition, since the conventional brown antenna uses a ground wire with a length of about λ / 4, the antenna is enlarged, and when used in a simple installation type base station, it protrudes sideways during assembly. There are problems such as injury on the ground.

  The present invention has been made to solve the above-described problems, and can extend the communication distance in the UHF band to cover a wide area and can be downsized, and can be safely used even in a simple installation type base station. An object of the present invention is to provide a dual-frequency antenna device that can be assembled.

  The dual-frequency antenna device according to the present invention includes a coaxial tube in which a tubular outer conductor and a center conductor are provided coaxially, and a UHF antenna provided on the upper side of the coaxial tube and connected to the center conductor of the coaxial tube. A radiating element, at least three first grounding elements arranged radially downward from an upper end of the coaxial pipe, and a predetermined distance below the first grounding element in the coaxial pipe. A second ground wire element having substantially the same shape as the first ground wire element, and a capacitor connected between the upper ends of the first and second ground wire elements and the outer conductor of the coaxial waveguide. A radiating element of a VHF antenna configured by setting an outer conductor of the coaxial tube to a predetermined length, first feeding means for feeding the radiating element of the UHF antenna through the coaxial tube, and the VHF The coaxial that forms the radiating element of the antenna Of and a second feeding means for feeding the external conductor, characterized in that it constitutes a monopole antenna with the ground line by the radiating element of the UHF antenna the first and second ground wire element.

  According to the present invention, even when the UHF antenna is arranged on the upper side of the VHF antenna, matching can be ensured by providing the two-stage ground wire element, and the broadband characteristic can be obtained. In addition, since the UHF antenna can be provided at a high position by being disposed on the upper side of the VHF antenna, a wide area can be covered by extending the communication distance in the UHF band.

  In addition, the VHF antenna can obtain the same effect as the capacitive element in which the two-stage ground element provided on the UHF antenna is loaded on the zenith, and can be lowered in size and reduced in size. Therefore, the length of the entire antenna can be shortened to form a small size, which can be easily transported and can be safely assembled, and can be configured to be used in a simple installation type base station.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a dual-frequency antenna device according to an embodiment of the present invention, and FIG. 2 is a side view of the dual-frequency antenna device.

  In FIGS. 1 and 2, reference numeral 20 denotes a matcher, which uses a metal matcher case 21, and the matcher case 21 is grounded via a pile 22. The matching unit 20 is provided with a VHF power supply plug 23 and a UHF power supply plug 24 on the side surface of the matcher case 21, and a pile mounting bracket 25 is mounted on the other side surface. The pile mounting bracket 25 is formed by being bent into a substantially L shape, and is attached to the side surface of the matcher case 21 so that the bent tip portion faces downward. The VHF power supply plug 23 and the UHF power supply plug 24 are each connected to a radio (not shown) via a power supply coaxial cable.

  On the other hand, the pile 22 is inserted into the ground when installing a simple installation type base station. For example, a plate-like member is bent at approximately 90 degrees when viewed from above, and a lower end thereof is sharply formed. Yes. Further, a joint fitting 26 bent in a substantially U-shape is attached to one side outer surface of the pile 22. The pile mounting bracket 25 provided on the matching unit case 21 of the matching unit 20 is pressure-input from above and joined to the inside of the connecting unit 26 so that the matching unit case 21 and the pile 22 are electrically connected. It has become. In this case, for example, a spring member is mounted on the inner side of the joining metal fitting 26, and when the pile attachment metal fitting 25 of the matching unit case 21 is inserted, the joining metal fitting 26 is crimped to ensure electrical connection.

  A VHF antenna 30 is mounted on the matching unit case 21, and a UHF antenna 40 is provided on the VHF antenna 30.

  The UHF antenna 40 is fed by a coaxial tube 31. The coaxial pipe 31 includes a tubular outer conductor 32 using a metal pipe and a bar-shaped central conductor 33 provided coaxially along the central axis of the outer conductor 32. The upper portion protrudes upward from the upper end by a length L1, and this protruding portion is used as a radiating element of the UHF antenna 40.

The outer conductor 32 of the coaxial tube 31 is used as a radiating element of the VHF antenna 30 and has a length of L2. The length of the UHF antenna 40 L1 is set to a length of about λ _M / 4, the length L2 of the VHF antenna 30 is set to a length of approximately λ _L / 8. Λ _M is the wavelength of the center frequency in the UHF band to be used, and λ _L is the wavelength of the lower end frequency in the VHF band to be used.

The ground wire element of the UHF antenna 40 is provided in two stages above the outer conductor 32 of the coaxial tube 31. That is, the upper insulating substrate 41a and the lower insulating substrate 41b are provided on the upper portion of the outer conductor 32 with an interval L3 of about λ _M / 4. Are radially provided at a predetermined angle, for example, an angle of about 30 degrees, at regular intervals, that is, at intervals of 120 degrees. The upper ground wire elements 42a to 42c have a length L4 of about λ _M / 4, and their upper ends are connected to the external conductor 32 via small-capacitance capacitors 43a to 43c as shown in FIG. FIG. 3 is a configuration diagram showing a connection relationship between the upper ground wire elements 42 a to 42 c (lower ground wire elements 44 a to 44 c) and the outer conductor 32 of the coaxial waveguide 31.

  The lower insulating substrate 41b is provided with lower ground wire elements 44a to 44c having a length L4 radially at equal intervals and at an angle of about 30 degrees. The upper ends of the lower ground wire elements 44a to 44c are connected to the external conductor 32 through small capacitors 45a to 45c in the same manner as the upper ground wire elements 42a to 42c. The upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c are formed in substantially the same shape.

  As described above, the UHF antenna 40 is provided with upper ground wire elements 42a to 42c and lower ground wire elements 44a to 44c in two stages with respect to the center conductor 33 protruding upward from the outer conductor 32 of the coaxial tube 31. The antenna is configured.

  The VHF antenna 30 is a monopole antenna using the outer conductor 32 of the coaxial tube 31 and the ground as a ground. In this case, the VHF antenna 30 can achieve the same effect as the capacitive element in which the upper ground line elements 42a to 42c and the lower ground line elements 44a to 44c of the UHF antenna 40 are loaded on the zenith part, and the attitude of the antenna can be lowered. Can do.

  In the matching unit case 21 of the matching unit 20, a VHF matching circuit 51 and a UHF matching circuit 52 are provided as shown in FIG. The VHF matching circuit 51 is connected to the VHF power supply plug 23 through a low pass filter (LPF) 53 that passes a VHF band signal, and the UHF matching circuit 52 includes a high pass filter (HPF) 54 that passes a UHF band signal. To the UHF power supply plug 24.

  On the upper surface of the matching unit case 21, an antenna joint 56 for mounting the antenna is provided. The antenna joint portion 56 includes a central conductor connection portion 57 and an external conductor connection portion 58, and the external conductor connection portion 58 is provided in a state of being insulated from the matcher case 21. The VHF matching circuit 51 is connected to the external conductor connecting portion 58, and the UHF matching circuit 52 is connected via a capacitor 61. Further, the external conductor connecting portion 58 is connected to the matching unit case 21 via the capacitor 62.

  The coaxial pipe 31 is attached to the antenna joint 56. In this case, the center conductor 33 led downward from the outer conductor 32 of the coaxial pipe 31 is connected to the center conductor connecting portion 57, and the outer conductor 32 is connected to the outer conductor connecting portion 58.

  That is, a signal in the VHF band supplied from the wireless device to the VHF power supply plug 23 of the matching unit 20 is passed through the low-pass filter 53, the VHF matching circuit 51, and the outer conductor connection portion 58 of the antenna joint portion 56. Power is supplied to (the outer conductor 32 of the coaxial tube 31). The UHF band signal supplied from the wireless device to the UHF power supply plug 24 of the matching unit 20 includes a high-pass filter 54, a UHF matching circuit 52, capacitors 61 and 62, an antenna junction 56 (a center conductor connection 57 and Power is supplied to the UHF antenna 40 through the outer conductor connecting portion 58) and the coaxial pipe 31 (the center conductor 33 and the outer conductor 32).

  In the above embodiment, the UHF antenna 40 has a two-stage structure in which the central conductor 33 protruding upward from the outer conductor 32 of the coaxial tube 31 is provided radially and obliquely downward from the upper end of the outer conductor 32 at equal intervals. Ground wire elements (upper ground wire elements 42a to 42c and lower ground wire elements 44a to 44c) constitute a monopole antenna with a ground wire (Brown antenna).

  Even when the UHF antenna 40 is arranged on the upper side of the VHF antenna 30 as described above, it is ensured by providing two stages of ground wire elements, that is, the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c. And broadband characteristics. By providing a single-stage ground element, that is, the upper ground elements 42a to 42c, matching is achieved at a specific resonance frequency, but it is difficult to realize a broadband characteristic. For this reason, the present embodiment provides a wide band characteristic in the UHF band by providing a two-stage ground wire element.

  When the ground element is one stage, the farther away from the resonance frequency, the more the radio wave cannot be reflected by the ground element, and the radiation from the radiation element decreases, and the power is transmitted through the outer conductor 32 of the coaxial tube 31. The phenomenon that returns to.

  However, by providing the ground wire elements in two stages, it is possible to radiate the electromagnetic wave that returns to the power source side through the outer conductor 32 of the coaxial waveguide 31 from the radiating element of the UHF antenna, so that the bandwidth can be increased.

  Further, since the UHF antenna 40 can be provided above the VHF antenna 30, that is, at a high position, the communication distance in the UHF band can be increased to cover a wide area.

  In general, the brown antenna is matched when the opening angle θ of the ground wire element is about 40 degrees. However, in the above embodiment, the upper ground wire elements 42a to 42c and the lower ground wire element 44a are used to reduce the size of the antenna. The opening angle θ of ˜44c is set to about 30 degrees. Even if the opening angle θ of the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c is set to about 30 degrees, it is possible to perform matching without any problem, thereby reducing the size of the antenna. .

On the other hand, the VHF antenna 30 constitutes a monopole antenna with the ground as the ground by using the outer conductor 32 of the coaxial tube 31 as a radiating element and grounding it via the pile 22. In addition, the VHF antenna 30 has the same effect as the capacitive element loaded on the zenith portion of the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c of the UHF antenna 40. be able to. Therefore, the VHF antenna 30 according to the above embodiment can be configured with a length of about λ _L / 8, which is about half that of a normal λ _L / 4 monopole antenna.

  The dual-frequency antenna device according to the above embodiment can be formed in a small size by shortening the entire length, so that it can be easily transported and can be assembled safely, and is suitable for use in a simple installation type base station. It can be configured.

  FIG. 5 shows the VSWR characteristics of the VHF antenna 30 according to the above embodiment. The horizontal axis represents f / fc (f is the frequency and fc is the center frequency), and the vertical axis is VSWR.

  FIG. 6 shows the VSWR characteristics of the UHF antenna 40 in the above embodiment, with the horizontal axis representing f / fc and the vertical axis representing VSWR.

  7 and 8 are for comparing the effects of capacitors 43a to 43c and 45a to 45c provided between the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c and the outer conductor 32 of the coaxial waveguide 31. FIG. It is the VSWR characteristic shown.

  FIG. 7 shows a case where the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c are short-circuited to the outer conductor 32 of the coaxial pipe 31, that is, without the capacitors 43a to 43c and 45a to 45c interposed. In the VSWR characteristics of the VHF antenna 30 when short-circuited, the horizontal axis indicates f / fc and the vertical axis indicates VSWR. When the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c are short-circuited to the outer conductor 32 of the coaxial pipe 31, the high frequency VSWR is deteriorated.

  FIG. 8 shows the VSWR characteristics of the UHF antenna 40 when the space between the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c and the outer conductor 32 of the coaxial waveguide 31 is open. The horizontal axis indicates f / fc. And the ordinate represents the VSWR. When the space between the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c and the outer conductor 32 of the coaxial waveguide 31 is opened, the frequency band is very narrow.

  When the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c and the outer conductor 32 of the coaxial waveguide 31 are short-circuited as described above, the VSWR characteristics of the VHF antenna 30 deteriorate, and the upper ground wire elements When the gaps between the outer conductors 32 of the coaxial pipe 31 are opened, the VSWR characteristics of the UHF antenna 40 are deteriorated.

  For this reason, in the present embodiment, the capacitors 43a to 43c and 45a to 45c are interposed between the upper ground wire elements 42a to 42c and the lower ground wire elements 44a to 44c and the outer conductor 32 of the coaxial waveguide 31, whereby FIG. As shown in FIG. 6, the VSWR characteristics of the VHF antenna 30 and the UHF antenna 40 are improved. That is, the VHF antenna 30 can improve the high frequency VSWR characteristics as shown in FIG. 5, and the UHF antenna 40 can be widened as shown in FIG. Can be kept below.

  FIG. 9 is a diagram showing the vertical plane directivity at the center frequency of the VHF band of the VHF antenna 30 and has a figure eight directivity. FIG. 10 shows the horizontal plane directivity at the center frequency of the VHF band of the VHF antenna 30 and is omnidirectional.

  FIG. 11 is a diagram showing the directivity characteristics of the UHF antenna 40 in the vertical plane at the center frequency of the UHF band. FIG. 12 shows the horizontal plane directivity at the center frequency of the UHF band of the UHF antenna 40, and is omnidirectional.

  In the above embodiment, the case where the center conductor 33 of the coaxial tube 31 protrudes from the upper end portion of the outer conductor 32 by a predetermined length to constitute the radiating element of the UHF antenna 40 has been described. A radiation element of a UHF antenna may be separately provided and connected to the central conductor 33.

  Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

1 is a perspective view of a dual frequency antenna device according to an embodiment of the present invention. It is a side view of the dual frequency antenna apparatus in the same embodiment. It is a block diagram which shows the connection relation between the ground wire element of the dual frequency shared antenna device and the outer conductor of the coaxial waveguide in the same embodiment. It is a figure which shows the circuit structure of the matching device in the same embodiment, and the electrical connection state of a matching device and a coaxial pipe | tube. It is a figure which shows the VSWR characteristic of the VHF antenna in the same embodiment. It is a figure which shows the VSWR characteristic of the UHF antenna in the embodiment. In the same embodiment, it is a figure which shows the VSWR characteristic of the VHF antenna at the time of short-circuiting between the upper ground wire element and a lower ground wire element, and the outer conductor of a coaxial waveguide. In the same embodiment, it is a figure which shows the VSWR characteristic of a UHF antenna at the time of opening between the upper ground element and lower ground element and the outer conductor of a coaxial pipe | tube. In the same embodiment, it is a figure which shows the vertical surface directional characteristic in the VHF band center frequency of a VHF antenna. In the same embodiment, it is a figure which shows the horizontal surface directivity characteristic in the VHF band center frequency of a VHF antenna. In the same embodiment, it is a figure which shows the vertical surface directional characteristic in the UHF band center frequency of a UHF antenna. In the same embodiment, it is a figure which shows the horizontal surface directivity characteristic in the UHF band center frequency of a UHF antenna. It is a side view which shows the structure of the conventional dual frequency shared antenna apparatus which has arrange | positioned the monopole-shaped UHF antenna and VHF antenna linearly in the orthogonal | vertical direction with respect to the earth.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Matching device, 21 ... Matching device case, 22 ... Pile, 23 ... VHF feeding plug, 24 ... UHF feeding plug, 25 ... Pile mounting bracket, 26 ... Joint fitting, 30 ... VHF antenna, 31 ... Coaxial Tube, 32 ... outer conductor, 33 ... center conductor, 40 ... UHF antenna, 41a ... upper insulating substrate, 41b ... lower insulating substrate, 42a-42c ... upper ground wire element, 43a-43c ... capacitor, 44a-44c ... lower ground Line elements, 45a to 45c ... capacitors, 51 ... VHF matching circuit, 52 ... UHF matching circuit, 53 ... low pass filter (LPF), 54 ... high pass filter (HPF), 56 ... antenna junction, 57 ... central conductor connection, 58: External conductor connection part, 61, 62: Capacitor.

Claims (1)

A coaxial tube in which a tubular outer conductor and a central conductor are provided coaxially, a radiating element of a UHF antenna provided on the upper side of the coaxial tube and connected to the central conductor of the coaxial tube, and obliquely from the upper end of the coaxial tube At least three first ground wire elements radially disposed below, and the first ground wire element provided in the coaxial pipe at a predetermined distance below the first ground wire element; A second ground wire element having substantially the same shape; a capacitor connected between the upper ends of the first and second ground wire elements and the outer conductor of the coaxial tube; A radiating element of the VHF antenna configured to have a length, a first feeding means for feeding the radiating element of the UHF antenna via the coaxial tube, and the coaxial tube constituting the radiating element of the VHF antenna. A second power supply means for supplying power to the outer conductor; Provided,
A dual-frequency antenna apparatus, wherein a grounded monopole antenna is constituted by the radiating element of the UHF antenna and the first and second ground line elements.

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